Digital data false alteration detection program and digital data false alteration detection apparatus

ABSTRACT

A digital data false alteration detection program causes a computer to execute (a) a step (S 1 ) of dividing digital data into a plurality of smaller block data, (b) a step (S 2 ) of extracting noise inherent to a digital data acquisition device for each of the small block data, (c) a step (S 3 ) of calculating correlation of the noise between adjacent small block data, and (d) a step (S 4 ) of detecting small block data having noise correlation lower than a level predetermined for the surrounding small block data, as falsely altered data.

TECHNICAL FIELD

The present invention relates to a program and an apparatus fordetecting a false alteration of digital data.

BACKGROUND OF THE INVENTION

An encryption technique called “the digital signature” is available as amethod of detecting a false alteration of digital data. In thistechnique, the genuineness of digital data is determined by collating ahash. Generally, the hash is collated by producing a hash from thecurrent data and comparing the particular hash with the original hashwritten in the header portion of the data.

This approach effectively functions in a completely closed system (asystem other than a general-purpose system, using a special data formatand having no fixed users), but cannot meet the requirement of an opensystem (a general-purpose system using an ordinary data format andassuming a multiplicity of unspecified users). This is by reason of thefact that once the file format is changed, the approach becomesinapplicable any longer.

Another approach called “the electronic watermark” is available. Thisconcerns a method in which data not related to digital contents areburied in the digital contents or in which the data buried are extractedand collated. The “electronic watermark” requires such a structure thatthe buried data are not easily erased by the process of editing,compression, transmission or conversion of the contents and that theburied data cannot be easily falsely altered or overwritten with falseinformation. In this method, the copyright information or the like, onceburied, can be extracted even from falsely altered data, and thereforethe originality of the data can be substantiated. Also, the falselyaltered position can be detected by comparing the falsely altered datawith the substantiated original data.

In this method, however, data are required to be buried in advance, andtherefore a device for burying the data is required. Also, the burieddata, which can be readily extracted as long as a burial method isknown, has a low durability. Further, the data burial unavoidablydeteriorates the data quality.

A digital image data acquisition device including an analog-to-digitalconverter, on the other hand, has a noise characteristic inherent to theanalog-to-digital (A/D) conversion process.

The output signal of the CCD providing a photoelectric conversiondevice, for example, is structurally known to contain noises typicallyincluding what is called a lead-out noise constituting the total noisesgenerated in a CCD element, an analog circuit of a control system and anA/D converter at the time of reading the charge of the CCD element and adark charge noise due to the dark current generated in a well under thephotoelectric surface of the CCD.

FIG. 1 is a diagram for explaining the noises contained in the output ofa CCD element. FIG. 1(A) shows a digital image picked up with a lens capattached to a digital camera which is frequency-converted using thetwo-dimensional FFT (Fast Fourier Transform), and FIG. 1(B) a solidlyblack digital image (O in digital value) produced using a digital imageediting program and frequency-converted by the two-dimensional FFT. FIG.1 indicates that the output data of the CCD element contains the noisesin composite fashion.

The digital image data acquisition device including the A/D converter,on the other hand, has a characteristic inherent to the pixel value ofthe digital image data in the A/D conversion process.

DISCLOSURE OF THE INVENTION

Accordingly, the problem of the present invention is to provide aprogram and an apparatus which works effectively even in an open systemby using a characteristic inherent to the A/D conversion process of adigital data acquisition device and detects a false alteration ofdigital data without any device for burying data in advance orextracting the buried data.

In order to solve the problem described above, according to a firstaspect of the invention, there is provided a digital data falsealteration detection program for causing a computer to detect the falsealteration of the digital data acquired by a digital data acquisitiondevice including a light detector or a sound detector and an A/Dconverter, characterized in that the computer is caused to execute:

-   -   (a) a step of dividing the digital data into at least two or        more small block data;    -   (b) a step of extracting a noise inherent to the digital data        acquisition device for each of the small block data;    -   (c) a step of calculating the correlation of the noises between        adjacent ones of the small block data; and    -   (d) a step of detecting small block data having a noise        correlation lower than a level predetermined for the surrounding        small block data, as a falsely altered data.

In the configuration according to the first aspect of the invention,preferably, the step (b) includes the step of converting each of thesmall block data into a frequency domain and extracting thehigh-frequency component of each small block data as a noise inherent tothe digital data acquisition device, or the step (b) includes the stepof converting each of the small block data into a frequency domain andextracting a specific high-frequency component of the small block dataas a noise inherent to the digital data acquisition device.

Also, preferably, the step (c) includes the step of calculating anaccumulated value of the noises for each of the small block data andcalculating the correlation of the noises from the difference of theaccumulated value of the noises between adjacent ones of the small blockdata.

Further, in order to solve the problem described above, according to asecond aspect of the invention, there is provided a digital data falsealteration detection apparatus for causing a programmed computer todetect a false alteration of the digital data acquired by a digital dataacquisition device including a light detector or a sound detector and anA/D converter, characterized by comprising a data divider for dividingthe digital data into at least two small block data, a noise extractionunit for extracting a noise inherent to the digital data acquisitiondevice for each of the small block data, and a false alterationdetection unit for calculating the correlation of the noise betweenadjacent ones of the small block data and detecting a small block datawith the noise correlation lower than a level predetermined for thesurrounding small block data, as falsely altered data.

In the configuration according to the second aspect of the invention,preferably, the noise extraction unit converts each of the small blockdata into a frequency domain and extracts the high-frequency componentof each small block data as a noise inherent to the digital dataacquisition device. As an alternative, the noise extraction unitconverts each of the small block data into a frequency domain andextracts a specific high-frequency component of each small block data asa noise inherent to the digital data acquisition device.

Also, preferably, the false alteration detection unit calculates anaccumulated value of the noises for each of the small block data andcalculates the correlation of the noises from the difference of theaccumulated value of the noises between adjacent ones of the small blockdata.

More preferably, the data divider is adapted to divide the small blockdata into data of an arbitrary size. Also, the data divider is adaptedto divide the digital data at an arbitrary position.

Also, in order to solve the problem described above, according to athird aspect of the invention, there is provided a digital image datafalse alteration detection program for causing a computer to detect afalse alteration of the digital image data acquired by a digital imagedata acquisition device including an A/D converter, characterized inthat the computer is caused to execute:

-   -   (a) the step of extracting the noise characteristic of the pixel        values of the digital image data; and    -   (b) the step of comparing the extracted noise characteristic        with the noise characteristic inherent to the A/D conversion        process of the digital image data acquisition device, and based        on the result of comparison, detecting a false alteration of the        digital image data acquired by the digital image data        acquisition device.

Also, in order to solve the problem described above, according to afourth aspect of the invention, there is provided a digital image datafalse alteration detection apparatus for causing a programmed computerto detect a false alteration of the digital image data acquired by adigital image data acquisition device including an A/D converter,characterized by comprising an image data noise characteristicextraction unit for extracting the noise characteristic of the pixelvalues of the digital image data, and an image data false alterationdetection unit for comparing the noise characteristic extracted by theimage data noise characteristic extraction unit with the noisecharacteristic inherent to the A/D conversion process of the digitalimage data acquisition device and based on the result of comparison,detecting a false alteration of the digital image data acquired by thedigital image data acquisition device.

Also, in order to solve the problem described above, according to afifth aspect of the invention, there is provided a digital image datafalse alteration detection program for causing a computer to detect afalse alteration of the digital image data acquired by a digital imagedata acquisition device including an A/D converter, characterized inthat the computer is caused to execute:

-   -   (a) the step of extracting the noise characteristic of the pixel        values of the digital image data; and    -   (b) the step of dividing the digital image data into at least        two small blocks, comparing the noise characteristics between        adjacent ones of the small blocks and upon development of an        anomaly between the compared noise characteristics, detecting a        false alteration of the digital image data acquired by the        digital image data acquisition device.

Also, in order to solve the problem described above, according to asixth aspect of the invention, there is provided a digital image datafalse alteration detection apparatus for causing a programmed computerto detect a false alteration of the digital image data acquired by adigital image data acquisition device including an A/D converter,characterized by comprising a noise characteristic extraction unit forextracting the noise characteristic of the pixel values of the digitalimage data, and a false alteration detection unit for dividing thedigital image data into at least two small blocks, comparing the noisecharacteristics between adjacent ones of the small blocks based on thenoise characteristic extracted by the noise characteristic extractionunit and upon development of an anomaly between the compared noisecharacteristics, detecting a false alteration of the digital image dataacquired by the digital image data acquisition device.

Also, in order to solve the problem described above, according to aseventh aspect of the invention, there is provided a digital image datafalse alteration detection program for causing a computer to detect afalse alteration of the digital image data acquired by a digital imagedata acquisition device including at least an A/D converter,characterized in that the computer is caused to execute:

(a) the step of extracting the characteristic about the pixel values ofthe digital image data; and

(b) the step of comparing the extracted characteristic with thecharacteristic inherent to the pixel value of the digital image data-inthe A/D conversion process of the digital image data acquisition deviceand based on the result of comparison, detecting a false alteration ofthe digital image data acquired by the digital image data acquisitiondevice.

In the configuration according to the seventh aspect of the invention,preferably, the step (a) includes the step of extracting a histogramabout the pixel values of the acquired digital image data, and the step(b) includes the step of comparing the extracted histogram with theinherent histogram about the pixel values of the digital image data inthe A/D conversion process of the digital image data acquisition device,and in the case where the inherent histogram assumes a continuous valuewhile the extracted histogram assumes a discontinuous value, detecting afalse alteration of the digital image data acquired by the digital imagedata acquisition device.

In the configuration according to the seventh aspect of the invention,preferably, the step (a) includes the step of dividing the acquireddigital image data into at least two equal small blocks and extractingthe array pattern of the pixel values of each small block, and the step(b) includes the step of detecting a false alteration of the digitalimage data in the case where the array patterns of the pixel values ofthe small blocks extracted in the step (a) are coincident with eachother, as compared with the inherent characteristic that the probabilitythat the array patterns of the pixel values of the small blocks coincidewith each other is very low.

In the configuration according to the seventh aspect of the invention,preferably, the digital image data acquisition device includes an imageacquisition device having a CCD, and the step (a) includes the step ofextracting the pixel value of each pixel of the acquired digital imagedata, while the step (b) includes the step of calculating a predictedpixel value of each pixel of the digital image data by interpolationbased on the CCD matrix array of the digital image data acquisitiondevice from the pixel value of each pixel of the digital image dataextracted in the step (a) and in the case where the pixel value of eachpixel extracted in the step (a) fails to coincide with a correspondingpredicted pixel value, detecting a false alteration of the digital imagedata.

Also, in order to solve the problem described above, according to aneighth aspect of the invention, there is provided a digital image datafalse alteration detection apparatus for causing a programmed computerto detect a false alteration of the digital image data acquired by adigital image data acquisition device including at least an A/Dconverter, characterized by comprising an image data characteristicextraction unit for extracting the characteristic about the pixel valuesof the digital image data, and an image data false alteration detectionunit for comparing the characteristic extracted by the image dataextraction unit with the characteristic inherent to the pixel value ofthe digital image data in the A/D conversion process of the digitalimage data acquisition device and based on the result of comparison,detecting a false alteration of the acquired digital image data.

In the configuration according to the eighth aspect of the invention,preferably, the image data characteristic extraction unit extracts ahistogram about the pixel values of the acquired digital image data, andthe image data false alteration detection unit compares the histogramextracted by the image data characteristic extraction unit with thehistogram inherent to the pixel values of the digital image data in theA/D conversion process of the digital image data acquisition device, andin the case where the inherent histogram assumes a continuous valuewhile the histogram extracted by the image data characteristicextraction unit assumes a discontinuous value, detects a falsealteration of the digital image data acquired by the digital image dataacquisition device.

In the configuration according to the eighth aspect of the invention,preferably, the image data characteristic extraction unit divides theacquired digital image data into at least two or more equal small blocksand extracts the array pattern of the pixel values of each small block,and the image data false alteration detection unit detects a falsealteration of the digital image data in the case where the arraypatterns of the pixel values of the small blocks extracted by the imagedata characteristic extraction unit are coincident with each other, ascompared with the inherent characteristic that the probability that thearray patterns of the pixel values of the small blocks coincide witheach other is very low.

In the configuration according to the eighth aspect of the invention,preferably, the digital image data acquisition device includes an imageacquisition device having a CCD, and the image data characteristicextraction unit extracts the pixel value of each pixel of the acquireddigital image data, while the image data false alteration detection unitcalculates a predicted pixel value of each pixel of the digital imagedata by interpolation based on the CCD matrix array of the digital imagedata acquisition device from the pixel value of each pixel of thedigital image data extracted by the image data characteristic extractionunit, and in the case where the pixel value of each pixel extracted bythe image data characteristic extraction unit fails to coincide with acorresponding predicted pixel value, detects a false alteration of thedigital image data.

Also, in order to solve the problem described above, according to aninth aspect of the invention, there is provided a digital image datafalse alteration detection program for causing a computer to detect afalse alteration of the digital image data acquired by a digital imagedata acquisition device, characterized in that the computer is caused toexecute:

the step of detecting a focused area in an image based on the digitalimage data, and upon determination that two or more areas are detectedand spaced from each other by at least a predetermined distance,detecting a false alteration of the digital image data.

Also, in order to solve the problem described above, according to atenth aspect of the invention, there is provided a digital image datafalse alteration detection system for causing a programmed computer todetect a false alteration of the digital image data acquired by adigital image data acquisition device, characterized by comprising afocused area detection unit for detecting focused areas in an imagebased on the digital image data, and a false alteration detection unitfor detecting a false alteration of the digital image data upondetermination, based on the positions, in the image, of the areasdetected by the focused area detection unit, that a plurality of theareas exist and are spaced from each other by a predetermined distance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining the output noises of a CCD device, inwhich (A) shows a digital image picked up by a digital camera with alens cap, as frequency-converted using the two-dimensional FFT, and (B)shows a solidly black digital image (zero in digital value) producedaccording to a digital image editing program, as frequency-convertedusing the two-dimensional FFT.

FIG. 2 is a flowchart of the digital data false alteration detectionprogram according to a first embodiment in the first aspect of theinvention.

FIG. 3 is a diagram showing a state in which a digital image is dividedinto small block images.

FIG. 4 is a diagram showing an example of the digital image, in which(A) shows a falsely altered digital image, and (B) an original digitalimage not falsely altered.

FIG. 5 is a graph showing an average accumulated value of thehigh-frequency components of the small block image in the digital imageversus the variations of the accumulated value of the high-frequencycomponents of the small block images, in which (A) corresponds to thedigital image of FIGS. 4(A) and (B) corresponds to FIG. 4(B).

FIG. 6 is a flowchart of a digital data false alteration detectionprogram according to another embodiment in the first aspect of theinvention.

FIG. 7 is a diagram showing a state in which a digital image is dividedinto small block images.

FIG. 8 is a graph showing the spectrum obtained by two-dimensional FFT.

FIG. 9 is a graph showing RMSE for each adjacent points, in which (A) isa graph corresponding to a falsely altered digital image, and (B) agraph corresponding to a digital image not falsely altered.

FIG. 10 is a flowchart of a digital data false alteration detectionprogram according to still another embodiment in the first aspect of theinvention.

FIG. 11 is a graph showing the RMSE value for each adjoining point, inwhich (A) to (D) correspond to a falsely altered digital image.

FIG. 12 is a graph showing the RMSE value for each adjoining point, inwhich (A) and (B) correspond to falsely altered digital data, and (C)corresponds to an original digital image not falsely altered.

FIG. 13 is a block diagram showing a general configuration of a digitaldata false alteration detection apparatus according to an embodiment inthe second aspect of the invention.

FIG. 14 is a graph showing an average accumulated value of thehigh-frequency components of the small blocks in the voice data obtainedby a computer versus the variations of the accumulated values of thehigh-frequency components of the small blocks, in which (A) correspondsto the falsely altered voice data and (B) corresponds to the originalvoice data.

FIG. 15 is a flowchart showing a digital image data false alterationdetection program according to an embodiment in the third aspect of theinvention.

FIG. 16(A) is a diagram showing a digital image picked up by a digitalcamera and not falsely altered.

FIG. 16(B) is a diagram showing the image of FIG. 16(A) processed foremphasizing the fluctuation of the least significant bit of the pixelvalue.

FIG. 17(A) is a diagram showing the image of FIG. 16(A) after falsealteration.

FIG. 17(B) is a diagram showing the image of FIG. 17(A) processed foremphasizing the fluctuation in the same manner as in FIG. 16(A).

FIG. 18 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the fourth aspect of the invention.

FIG. 19 is a flowchart showing a digital image data false alterationprogram according to an embodiment in the fifth aspect of the invention.

FIG. 20 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the sixth aspect of the invention.

FIG. 21 is a flowchart showing a digital image data false alterationprogram according to an embodiment in the seventh aspect of theinvention.

FIG. 22 is a flowchart showing a digital image data false alterationprogram according to another embodiment in the seventh aspect of theinvention.

FIG. 23(A) is a diagram showing a digital image picked up by a digitalcamera and not falsely altered.

FIG. 23(B) is a diagram showing a histogram about the pixel values ofthe image shown in FIG. 23(A).

FIG. 24(A) is a diagram showing the image of FIG. 23(A) falsely alteredby the gradation conversion process.

FIG. 24(B) is a diagram showing a histogram about the pixel values ofthe image of FIG. 24(A).

FIG. 25 is a flowchart showing a digital image data false alterationdetection program according to still another embodiment in the seventhaspect of the invention.

FIG. 26(A) is a diagram showing a digital image picked up by a digitalcamera and not falsely altered.

FIG. 26(B) is a diagram showing an image falsely altered by stamping theimage of FIG. 26(A).

FIGS. 27(A) to (D) are diagrams showing array patterns of the imageportions 1 to 4 in FIG. 26(B) after equally dividing the image of FIG.26(B) into small blocks and extracting the array pattern of the pixelvalues of the small blocks.

FIG. 28 is a flowchart showing a digital image data false alterationdetection program according to yet another embodiment in the seventhaspect of the invention.

FIG. 29 is a diagram showing a CCD matrix.

FIG. 30(A) is a diagram showing an example of the pixel values detectedby a portion of the CCD matrix shown in FIG. 29.

FIG. 30(B) is a list of the CCD devices of a portion of the CCD matrixof FIG. 29 which are numbered by way of explanation.

FIG. 31(A) is a diagram showing the pixel values of a digital imagepicked up with a portion of the CCD matrix shown in FIG. 29 and notfalsely altered.

FIG. 31(B) is a diagram showing the pixel values of the image of FIG.31(A) falsely altered by the Gaussian shading.

FIG. 32(A) is a diagram showing the pixel values assumed to have beendetected by the corresponding CCD devices from the pixel values shown inFIG. 31(B).

FIG. 32(B) is a diagram showing the predicted pixel values calculatedfrom the pixel values shown in FIG. 32(A).

FIG. 33 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the eighth aspect of the invention.

FIG. 34 is a flowchart showing a digital image data false alterationdetection program according to an embodiment in the ninth aspect of theinvention.

FIG. 35 is a diagram showing a digital image picked up by a digitalcamera and not falsely altered.

FIG. 36 is a graph showing the frequency characteristic obtained usingHPF by performing FFT of 16×16 pixels extracted from the focused area P4in the image shown in FIG. 35.

FIG. 37 is a graph showing the frequency characteristic obtained by theprocess similar to that for the area P4 by extracting 16×16 pixels fromthe unfocused area P5 making up the background of the image shown inFIG. 35.

FIG. 38 is a diagram showing the image of FIG. 35 falsely altered bysynthesis with another image.

FIG. 39 is a graph showing the frequency characteristic obtained by asimilar process to that for the area P4 of FIG. 35 by extracting 16×16pixels from the area P6 of another image synthesized in the image shownin FIG. 38.

FIG. 40 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according an embodimentin the tenth aspect of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the invention are described below withreference to the accompanying drawings. FIG. 2 is a flowchart of thedigital data false alteration detection program according to anembodiment in the first aspect of the invention. According to thisembodiment, the digital data is formed of a digital image. With thedigital data false alteration detection program according to thisinvention, the computer first divides the digital image of which a falsealteration is to be detected, into a plurality of small block images bya computer, as shown in FIG. 3 (step S1 in FIG. 2). In this example, asapparent from FIG. 3, the digital image is divided into eight smallblocks in horizontal direction and five small blocks in verticaldirection for a total of 40 small block images B001 to B040.

Next, each of the small block images divided in step S1 is convertedinto a frequency domain using the two-dimensional FFT (Fast FourierTransform) by the computer, and the low-frequency component is cut offby a high-pass filter while amplifying the high-frequency component(step S2 in FIG. 2). The accumulated value of the high-frequencycomponent is determined for each small block image (step S3 in FIG. 2).Further, the accumulated value of each small block image is compared,and a small block image having an anomalous value is detected as afalsely altered image (step S4 in FIG. 2). In step S4, preferably, theaverage of the accumulated value of the small block images iscalculated, and the absolute value of the difference between theaccumulated value and the average value divided by the standarddeviation is calculated for each small block image, so that a block 3 ormore off in standard deviation is detected as a small block image havingan anomalous value.

As a specific example, an explanation is given about a case in which adigital data false alteration detection program according to thisinvention is installed in the computer and used for the digital imageactually picked up by a digital camera. FIG. 4(B) shows an example ofthe digital image picked up by a digital camera and not falsely altered,and FIG. 4(A) the digital image of FIG. 4(B) partially “shaded”according to the digital image editing program. In FIG. 4(A), referencenumeral 10 designates a portion subjected to the “shading” process. Theportion 10 in FIG. 4(A) corresponds to the small block image B019 inFIG. 3.

FIG. 5 is a graph showing the average accumulated value of thehigh-frequency components of the small block images of the digital imageversus the variation of the accumulated value of the high-frequencycomponent of each small block image, obtained by the computer. (A)corresponds to the digital image of FIGS. 4(A), and (B) corresponds toFIG. 4(B). In FIG. 5, the ordinate represents the absolute value of thedifference between the average accumulated value of the small blockimaged and the accumulated value of each small block image divided bythe standard deviation, and the abscissa the number of each small block.As apparent from FIG. 5, the block B019 of which the data is falselyaltered may be detected as a block of an anomalous accumulated value ofthe high-frequency component.

In this way, with the digital data false alteration detection programaccording to this invention, the computer is caused to detect a falsealteration, if any, based on the noises mixed at the time of acquisitionof the digital image. Therefore, a false alteration of the digital imagecan be detected without using a device for adding extraneous data suchas an electronic watermark to the digital image of which a falsealteration is to be detected.

FIG. 6 is a flowchart for the digital data false alteration detectionprogram according to another embodiment in the first aspect of theinvention. In this embodiment, the digital data is formed of a digitalimage. With the digital data false alteration detection programaccording to this aspect of this invention, the computer first dividesthe digital image of which a false alteration is to be detected, into aplurality of small block images as shown in FIG. 7 (step S1 in FIG. 6).In this example, as apparent from FIG. 7, the digital image is dividedinto four blocks in horizontal direction and three blocks in verticaldirection for a total of 12 small block images B001 to B012. Also, thesmall block images are adjacent to other small block images at theadjoining points C001 to C017, respectively.

Next, the computer converts each of the small block images into whichthe digital image is divided in step S1, into a frequency domain usingthe two-dimensional FFT (step S2 in FIG. 6). FIG. 8 is a graph of thespectrum obtained by the two-dimensional FFT. In FIG. 8, the center peak20 represents a DC component, and the higher the frequency, the fartherfrom the peak 20.

The computer smoothes a specific frequency component of all the smallblock images B001 to B012 and thus calculates a noise spectrum (step S3in FIG. 6). In smoothing a specific frequency component, frequencyvectors 23, 24, 25 in a specific domain are picked out and averaged outalong the ordinate 21 in FIG. 8, so that a spectrum 26 representing theparticular domain is obtained. Also, along the abscissa 22, frequencyspectra 27, 28, 29 in a specific domain are picked out and averaged out,so that a noise spectrum 30 representing the particular domain isobtained.

Further, the computer determines the Euclidean distance (RMSE: Root MeanSquare Error), for each of the adjoining points C001 to C017, of thenoise spectrum between adjoining blocks at the particular adjoiningpoint and detects the block surrounded by adjoining points having ananomalous RMSE value, as a falsely altered block (step S4 in FIG. 6).

As a specific example, an explanation is given about a case in which thedigital data false alteration detection program according to theinvention is installed in the computer and used for a digital imageactually picked up by a digital camera. Also in this case, the samedigital image as FIG. 4(B) is used as a digital image not falselyaltered. On the other hand, a part of the digital image shown in FIG.4(B), which is subjected to “the shading” process by the digital imageediting program at a position corresponding to the block B007 in FIG. 7,is used as a digital image falsely altered.

FIG. 9 is a graph showing the RMSE for each adjoining point determinedin step S4. (A) is a graph corresponding to a digital image falselyaltered, and (B) a graph corresponding a digital image not falselyaltered. In FIG. 9, the ordinate represents the RMSE value, and theabscissa the number of each adjoining point. As apparent from FIG. 9,the block B007 surrounded by the adjoining points C006, C009, C010, C013having an anomalous RMSE value can be detected as a block with a falselyaltered data.

Also in this embodiment, similar effects to the embodiment shown in FIG.2 are obtained.

FIG. 10 is a flowchart for the digital data false alteration detectionprogram according to another embodiment in the first aspect of theinvention. With the digital data false alteration detection programaccording to this aspect of the invention, the computer first dividesthe digital image of which a false alteration, if any, is to bedetected, into a plurality of small block images as shown in FIG. 7, inthe same manner as in the embodiment shown in FIG. 6 (step S1 in FIG.10). Next, the computer converts each of the small blocks divided instep S1 into a frequency domain using the two-dimensional FFT (step S2in FIG. 10). As the result of this two-dimensional FFT, as in the caseof the embodiment shown in FIG. 6, a graph of spectrum as shown in FIG.8 is obtained.

Then, the computer smoothes a specific frequency component, in the samemanner as in the embodiment shown in FIG. 6, for all the small blockimages B001 to B012 thereby to calculate a noise vector (step S3 in FIG.10). After that, for each adjoining point, the Euclidean distance (RMSE)of the noise vector between the blocks adjoining the particularadjoining point, and a block with the RMSE value surrounded by theanomalous adjoining points is detected as a falsely altered block (stepS4 in FIG. 10). In the case where no anomalous adjoining point isdetected, the computer changes both the size of the divided block andthe position of dividing the digital image thereby to move the dividedblock (step S5 in FIG. 10). Then, steps S1 to S4 are repeated.

As a specific example, a case is explained in which the digital datafalse alteration detection program according to the invention isinstalled in the computer and used actually for the digital image pickedup by a digital camera. Also in this example, the same digital image asin FIG. 4(B) is used as a digital image not falsely altered. A part ofthe digital image of FIG. 4(B), which is subjected to the “shading”process by the digital image editing program at a position correspondingto the block B007 in FIG. 7, for example, is used as a digital imagefalsely altered. FIGS. 11 and 12 are graphs showing the RMSE value foreach adjoining point determined in step S4. FIG. 11(A) is a graph inwhich the “shading” process covers the blocks B002, B003, B006, B007 inthe digital image falsely altered, FIG. 11(B) a graph in which the“shading” process covers the blocks B003, B004, B007, B008 in thedigital image falsely altered, FIG. 11(C) a graph in which the “shading”process covers the blocks B005, B006 in the digital image falselyaltered, and FIG. 11(D) a graph in which the “shading” process coversthe blocks B007, B008 in the digital image falsely altered. Also, FIG.12(A) is a graph in which the “shading” process covers only the blockB007 in the digital image falsely altered, FIG. 12(B) a graph in whichthe “shading” process covers the blocks B007, B008 in the digital imagefalsely altered, and FIG. 12(C) a graph corresponding to the digitalimage not falsely altered.

As seen from FIGS. 11 and 12, an adjoining point having an anomalousRMSE value is detected in the case of FIG. 12(A), in which a block withthe data thereof falsely altered can be detected by moving the dividedblocks.

Although the digital image is converted to a frequency domain by FFT inall the embodiments described above, the digital image can be convertedto a frequency domain alternatively by the wavelet conversion, DCT(Discrete Cosine Transform) or DST (Discrete Sine Transform) with equaleffect.

FIG. 13 is a block diagram showing a general configuration of a digitaldata false alteration detection apparatus according to a firstembodiment in the second aspect of the invention. The apparatusaccording to this aspect of the invention comprises, as shown in FIG.13, a programmed computer, a data divider 40 for dividing the digitaldata into a plurality of small block data, a noise extraction unit 41for extracting a noise inherent to the digital data acquisition devicefor each small block data, and a false alteration detection unit 42 forcalculating a noise correlation between adjoining small block data anddetecting small block data having a noise correlation lower than a levelpredetermined for the surrounding small block data, as falsely altereddata.

The noise extraction unit 41 converts each of the small block data intoa frequency domain and extracts the high-frequency component of eachsmall block data as a noise inherent to the digital data acquisitiondevice, or converts each of the small block data into a frequency domainand extracts a specific frequency component of each small block data asa noise inherent to the digital data acquisition device.

The false alteration detection unit 42 calculates an accumulated valueof noises for each small block data, and thus calculates a noisecorrelation from the difference of the accumulated noise value betweenthe adjoining small block data.

The data divider 40 is adapted to divide the small block data intoblocks of an arbitrary size and the digital data at an arbitraryposition.

According to still another embodiment in this aspect of the invention,the digital data false alteration detection program according to theinvention is used for the digital sound data. As compared with theembodiment of FIG. 2 in which the data are two-dimensionally processed,this embodiment is different only in that the data are processedone-dimensionally.

In this embodiment, therefore, the digital data false alterationdetection program according to the invention has a flow similar to thatof FIG. 2. By use of the digital data false alteration detection programaccording to this invention, the computer first divides the digitalsound data of which a false alteration is to be detected, into aplurality of small blocks. In the example under consideration, thedigital sound data are divided into 132 parts one-dimensionally for atotal of 132 small blocks D001 to D132.

Next, the computer converts each small block division to a frequencydomain using the one-dimensional FFT, while at the same time cutting offthe low-frequency component thereof with a high-pass filter thereby toamplify the high-frequency component. Then, an accumulated value of thehigh-frequency component is determined for each small block. Further,the average accumulated value of each small block is calculated, and bycalculating the absolute value of the difference between the accumulatedvalue and the average value, divided by the standard deviation, eachblock with the standard deviation different by 3 or more is detected asa block having an anomalous value.

As a specific example, an explanation is given of a case in which thedigital data false alteration detection program according to theinvention is installed in the computer and used for the voice dataactually recorded by microphone. The voice data synthesized by thecomputer and mixed at a position corresponding to the block D028 of theoriginal voice data recorded is used as a falsely altered voice data.

FIG. 14 is a graph, obtained by the computer, showing the averageaccumulated value of the high-frequency component of the small blocks ofthe voice data versus the variation of the accumulated value of thehigh-frequency component of each small block image. (A) corresponds tothe voice data falsely altered, and (B) corresponds to the originalvoice data. In FIG. 14, the ordinate represents the absolute value ofthe difference between the average accumulated value of the small blocksand the accumulated value of each small block, divided by the standarddeviation, and the abscissa the number of each small block. As apparentfrom FIG. 14, the block B028 of which the data is falsely altered may bedetected as a block having an anomalous accumulated value of thehigh-frequency component.

FIG. 15 is a flowchart of the digital image data false alterationdetection program according to an embodiment in the third aspect of theinvention. As shown in FIG. 15, with the digital image data falsealteration detection program according to the invention, the computerfirst extracts the noise characteristic of the pixel value of thedigital image data of which a false alteration is to be detected,acquired by the digital image data acquisition device including ananalog-to-digital converter (A/D converter) (step S1 in FIG. 15). Next,the computer compares the noise characteristic extracted in step S1 withthe noise characteristic inherent to the A/D conversion process in thedigital image data acquisition device, and based on the result ofcomparison, detects a false alteration of the digital image dataacquired by the digital image data acquisition device (step S2 in FIG.15).

As a specific example, an explanation is given of a case in which thedigital image data alteration detection program according to theinvention is installed in the computer and used for the digital imageactually picked up by a digital camera. In this case, the noisecharacteristic can be detected by checking the least significant bit ofthe pixel value of the digital image data. Nevertheless, it is alsopossible to extract the noise characteristic by other appropriatewell-known methods. FIG. 16(A) shows a digital image not falselyaltered, picked up by a digital camera, and FIG. 16(B) an image obtainedby processing the digital image shown in FIG. 16(A) for emphasizing thefluctuation of the least significant bit of the pixel value. Accordingto this embodiment, in the case where the least significant bit of thepixel value of the original digital image is 0, the pixel value of theparticular pixel is held as it is, while in the case where the leastsignificant bit is 1, the pixel value of the particular pixel isreplaced with 255 thereby to emphasize the fluctuation. FIG. 17(A) showsan image falsely altered from the image shown in FIG. 16(A) by attachinga copy of a part of the image portion around the image portion P1 ofFIG. 16(A) to a part of the image portion P1, and FIG. 17(B) the imageof FIG. 17(A) processed for emphasizing the fluctuation in a similarmanner to FIG. 16(A).

Due to the noise characteristic inherent to the A/D conversion processof the digital image data acquisition device, a normal digital imagecontains noises at random, and the distribution of the least significantbit of the pixel value is substantially random, so that the fluctuationappears at random. As shown in FIG. 16(B), therefore, after the processof emphasizing the fluctuation of the digital image not falsely altered,the image contains substantially no solidly black area. As understoodfrom FIG. 17(B), however, once an image is falsely altered, the noisecontained in the image portion falsely altered becomes uniform and thefluctuation is smoothed, thereby the falsely altered image portion issolidly blackened. In this way, the falsely altered image of FIG. 17(B)is detected by comparing FIG. 16(B) and FIG. 17(B) with each other.

FIG. 18 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the fourth aspect of the invention. As shown in FIG. 18,the digital image data false alteration detection apparatus according tothis invention comprises a programmed computer, an image data noisecharacteristic extraction unit 50 for extracting the noisecharacteristic of the pixel value of the digital image data acquired bythe digital image data acquisition device including an analog-to-digitalconverter (A/D converter), and an image data false alteration detectionunit 51 for comparing the noise characteristic extracted by the imagedata noise characteristic extraction unit 50 with the noisecharacteristic inherent to the A/D conversion process of the digitalimage data acquisition device, and based on the result of comparison,detecting a false alteration of the digital image data acquired by thedigital image data acquisition device.

FIG. 19 is a flowchart of the digital image data false alterationdetection program according to an embodiment in the fifth aspect of theinvention. As shown in FIG. 19, with the digital image data falsealteration detection program according to the invention, the computerfirst extracts the noise characteristic of the pixel value of thedigital image data acquired by the digital image data acquisition device(step S1 in FIG. 19). Next, the computer divides the digital image datainto at least two small blocks and compares the noise characteristicbetween adjoining small blocks, and in the case where an anomalydevelops between the noise characteristics compared, detects a falsealteration of the digital image data acquired by the digital image dataacquisition device (step S2 in FIG. 19).

FIG. 20 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the sixth aspect of the invention. As shown in FIG. 20,the digital image data false alteration detection apparatus according tothis invention comprises a programmed computer, a noise characteristicextraction unit 60 for extracting the noise characteristic of the pixelvalue of the digital image data acquired by the digital image dataacquisition device, and a false alteration detection unit 61 fordividing the digital image data into at least two small blocks,comparing the noise characteristics of the adjoining small blocks witheach other based on the noise characteristic extracted by the noisecharacteristic extraction unit 60, and in the case where an anomalyappears between the compared noise characteristics, detecting a falsealteration of the digital image data acquired by the digital image dataacquisition device.

FIG. 21 is a flowchart of the digital image data false alterationdetection program according to an embodiment in the seventh aspect ofthe invention. As shown in FIG. 21, with the digital image data falsealteration detection program according to the invention, the computerfirst extracts the noise characteristic of the pixel value of thedigital image data of which a false alteration is to be detected,acquired by the digital image data acquisition device including an A/Dconverter (step S1 in FIG. 21). Next, the computer compares the noisecharacteristic extracted in step S1 with the noise characteristicinherent to the pixel value of the digital image data in the A/Dconversion process of the digital image data acquisition device, andbased on the result of comparison, detects a false alteration of thedigital image data acquired by the digital image data acquisition device(step S2 in FIG. 21).

In this case, the characteristic of the pixel value of the digital imagedata and the characteristic inherent to the pixel value of the digitalimage data in the A/D conversion process of the digital imageacquisition device are various.

FIG. 22 is a flowchart of a digital image data false alterationdetection program according to another embodiment in the seventh aspectof the invention. This embodiment takes into consideration a histogramas a characteristic of the pixel value of the digital image data and acharacteristic of the pixel value of the digital image data in the A/Dconversion process of the digital image data acquisition device.Specifically, according to this embodiment, as shown in FIG. 22, withthe digital image data false alteration detection program, the computerfirst extracts a histogram of the pixel value of the digital image dataof which a false alteration is to be detected (step S10 in FIG. 22).Next, the computer compares the extracted histogram with the histogramunique to the pixel value of the digital image data in the A/Dconversion process of the digital image data acquisition device and inthe case where the extracted histogram assumes a discontinuous valuewhile the inherent histogram assumes a continuous value, detects a falsealteration of the digital image data acquired by the digital image dataacquisition device (step S11 in FIG. 22).

This embodiment is effective especially for detecting a false alterationby the gradation conversion process of the digital image data.

As a specific example, an explanation is given about a case in which adigital image data false alteration detection program according to thisinvention is installed in the computer and used for the digital imageactually picked up by a digital camera. FIG. 23(A) shows an example ofthe digital image picked up by a digital camera and not falsely altered,and FIG. 24(A) the digital image of FIG. 23(A) falsely altered by thegradation conversion of the digital image shown in FIG. 23(A). FIG.23(B) shows a histogram of the pixel value of the digital image shown inFIG. 23(A), and FIG. 24(B) a histogram of the pixel value of the digitalimage shown in FIG. 24(A). In FIGS. 23(B) and 24(B), the abscissa of thegraph represents the gradation value and the ordinate the frequency.

As shown in FIG. 23(B), the histogram inherent to the pixel value of thedigital image data in the A/D conversion process of the digital imageacquisition device assumes a continuous value. Once the digital imagedata acquired by the digital image acquisition device is falselyaltered, on the other hand, the histogram of the pixel value of theparticular image data assumes a discontinuous value as shown in FIG.24(B). In the case where the histogram assumes a discontinuous value,therefore, a false alteration of the digital image data can be detected.

This example concerns the case of a digital image in gray scale. As analternative, a false alteration of a RGB digital image can also bedetected in a manner similar to the gray scale image by producing ahistogram for each channel of R, G, B.

FIG. 25 is a flowchart for a digital image data false alterationdetection program according to still another embodiment in the seventhaspect of the invention. According to this embodiment, the array patternof the pixel values for each of the small blocks into which the digitalimage data with a false alteration thereof to be detected is divided isconsidered as a characteristic of the pixel value of the digital imagedata, and compared with the characteristic inherent to the digital imagedata acquisition device. Specifically, in this embodiment, with thedigital image data false alteration detection program according to theinvention, as shown in FIG. 25, the computer first divides the digitalimage data of which a false alteration is to be detected, into at leasttwo or more small equal blocks, and extracts an array pattern of thepixel values for each small block (step S20 in FIG. 25). Next, thecomputer detects a false alteration of the digital image data in thecase where the array patterns of the pixel values of the small blocksextracted in step S20 coincide with each other in spite of thecharacteristic fact of the pixel value of the digital image data in theA/D conversion process of the digital image data acquisition device tothe effect that the probability is very low that the array patterns ofthe pixel values of the small blocks coincide with each other (step S21in FIG. 25).

This embodiment is effective especially for detecting a false alterationof the digital image data by stamping.

As a specific example, an explanation is given about a case in which thedigital image data false alteration detection program according to theinvention is installed in the computer and used for the digital imageactually picked up by a digital camera. FIG. 26(A) shows an example ofthe digital image picked up by a digital camera and not falsely altered,and FIG. 26(B) an image falsely altered by stamping from the image shownin FIG. 26(A). In the stamping process, as shown in the image of FIG.26(B), an image portion 1 configured of 3 by 3 pixels is copied andattached to an image portion 2 (corresponding to the image portion P2 inFIG. 26(A)) configured of 3 by 3 pixels. Similarly, an image portion 3configured of 3 by 3 pixels is copied and attached to an image pixelportion 4 (corresponding to the image portion P3 in FIG. 26(A))configured of 3 by 3 pixels.

FIGS. 27(A) to (D) show array patterns of the pixel values of the imageportions 1 to 4 extracted from the equal small blocks of 3 by 3 pixelsinto which the digital image is divided. As understood from FIG. 27, thearray patterns of the pixel values coincide between the image portion 1(FIG. 27(A)) and the image portion 2 (FIG. 27(B)), and the arraypatterns of the pixel values coincide between the image portion 3 (FIG.27(C)) and the image portion 4 (FIG. 27(D)). As a result, a falsealteration of the digital image data can be detected which has beencarried out by executing the stamping process between the image portions1 and 2 on the one hand, and between the image portions 3 and 4 on theother hand.

This example represents a case concerning the gray scale digital image.Nevertheless, a false alteration of a RGB digital image can also bedetected in a manner similar to the gray scale image by extracting thearray pattern of the pixel values for each channel of R, G, B in smallblocks.

FIG. 28 is a flowchart for a digital image data false alterationdetection program according to yet another embodiment in the seventhaspect of the invention. This embodiment is applicable to a digitalimage data acquisition device having a CCD such as a digital camera oran image scanner. As shown in FIG. 28, with the digital image data falsealteration detection program according to this invention, the computerfirst extracts the pixel value of each pixel of the digital image ofwhich a false alteration is to be detected, acquired by the digitalimage acquisition device including an A/D converter (step S30 in FIG.28).

Next, the computer calculates a predicted pixel value of each pixel ofthe digital image data by the interpolation calculation based on thearray of the CCD matrix of the digital image data acquisition devicefrom the pixel value of each pixel of the digital image data extractedin step S30, and in the case where the pixel value of a given pixelextracted in step S30 fails to coincide with a corresponding predictedpixel value, detects a false alteration of the digital image data (stepS31 in FIG. 28). Step S31 is explained in detail below.

A digital camera, an image scanner, etc. having a CCD, as shown in FIG.29, normally comprises a CCD matrix of CCD devices 100 to 102 having R(red), G (green) and B (blue) filters, respectively, arranged in apredetermined pattern. The CCD devices 100 to 102 of the CCD matrix eachcorrespond to a pixel of the digital image. In this state, however, eachpixel has a pixel value of only one channel of R, G or B (a pixelcorresponding to the CCD device having the R filter, for example, hasonly a R value), and therefore, an appropriate digital image cannot beretrieved. In view of this, pixel values of non-existent channels (thevalues of G and B for the pixel corresponding to the CCD device havingthe R filter, for example) are calculated by interpolation for each CCDdevice from the surrounding pixel values of the same channel. Severalmethods are available for interpolation calculation. Assuming that theaveraging method is employed in this case, the interpolation calculationis carried out in the following manner.

Specifically, assume that the interpolation calculation is carried outfor the portion 200 including 4 by 4 CCD devices in the CCD matrix shownin FIG. 29, and that each CCD device of the portion 200 has detected apixel value shown in FIG. 30(A). Incidentally, FIG. 30(B) is a list ofthe numbers attached to the CCD devices of the portion 200 to facilitateexplanation.

The pixel values of the pixels corresponding to the CCD devices 6, 7, 10and 11 shown in FIG. 30(B) are determined by interpolation calculationin the following manner:

(1) Pixels Corresponding to the CCD Device 6

The R value is determined by averaging the R values of the CCD devices1, 3, 9 and 11. Specifically, R=(0+0+0+255)/4=63.75. The G value, on theother hand, is determined by averaging the G values of the pixels 2, 5,7 and 10. Specifically G=(0+0+255+255)/4=127.5. The B value remains asit is, that is, B=0.

(2) Pixels Corresponding to the CCD Device 7

The R value is determined by averaging the R values of the CCD devices 3and 11. Specifically, R=(0+255)/2=127.5. The G value remains as it is,that is, G=0. The B value, on the other hand, is determined by averagingthe B values of the CCD devices 6 and 8. Specifically B=(0+255)/2=127.5.

(3) Pixels Corresponding to the CCD Device 10

The R value is determined by averaging the R values of the CCD devices 9and 11. Specifically, R=(0+255)/2=127.5. The G value remains as it is,that is, G=0. The B value, on the other hand, is determined by averagingthe B values of the CCD devices 6 and 14. SpecificallyB=(0+255)/2=127.5.

(4) Pixels Corresponding to the CCD Device 11

The R value remains as it is, that is, R=0. The G value is determined byaveraging the G values of the CCD devices 7, 10, 12 and 15.Specifically, (255+255+0+0)/4=127.5. The B value, on the other hand, isdetermined by averaging the B values of the CCD devices 6, 8, 14 and 16.Specifically, (0+255+255+0)/4=127.5.

This interpolation calculation is carried out for all the CCD devicesmaking up the portion 200 thereby to determine the pixel value of eachpixel of a corresponding digital image as shown in FIG. 31(A).

In this case, the pixel value of the filter of the CCD device is notchanged by the interpolation calculation. As long as the arrangement ofthe CCD matrix and the method of interpolation calculation are known inadvance, therefore, the pixel value (predicted pixel value) that a givendigital image data should originally hold can be calculated from thepixel value of the particular digital image data. Unless the digitalimage data is falsely altered, the original pixel value and thepredicted pixel value of the digital image data naturally coincide witheach other. In the case where the original pixel value and the predictedpixel value fail to coincide with each other, therefore, a falsealteration of the image data is detected.

This embodiment is effective for detecting a false alteration of thedigital image data committed by any of various well-known falsealteration methods.

As a specific example, an explanation is given below about a case inwhich the digital image data false alteration detection programaccording to this invention is installed in a computer and used for adigital image actually picked up by a digital camera.

The digital camera is assumed to have the CCD matrix shown in FIG. 29.FIG. 31(B) shows the pixel values extracted from the image falselyaltered by the Gaussian shading process executed on the image shown inFIG. 31(A). FIG. 32(A) shows the pixel values assumed to have beendetected from the pixel values of FIG. 31(B) by the corresponding CCDdevices. FIG. 32(B) shows the predicted pixel values calculated from thepixel values of FIG. 32(A). The pixel values of FIG. 31(B) fail tocoincide with the predicted pixel values of FIG. 32(B), and therefore afalse alteration of the digital image is detected.

FIG. 33 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the eighth aspect of the invention. The digital image datafalse alteration detection apparatus according to this inventioncomprises a programmed computer, an image data characteristic extractionunit 70 for extracting the characteristic of the pixel values of thedigital image data acquired by the digital image acquisition deviceincluding an A/D converter, and an image data false alteration detectionunit 71 for comparing the characteristic extracted by the image datacharacteristic extraction unit 70 with the characteristic inherent tothe pixel values of the digital image data in the A/D conversion processof the digital image data acquisition device, and based on the result ofcomparison, detecting a false alteration of the digital image data.

According to another embodiment in the eighth aspect of the invention,the image data characteristic extraction unit 70 extracts a histogram ofthe pixel values of the digital image data. The image data falsealteration detection unit 71 compares the histogram extracted by theimage data characteristic extraction unit 70 with the histogram inherentto the pixel values of the digital image data in the A/D conversionprocess of the digital image data acquisition device, and in the casewhere the inherent histogram assumes a continuous value while thehistogram extracted by the image data characteristic extraction unit 70assumes a discontinuous value, detects a false alteration of the digitalimage data acquired by the digital image data acquisition device.

According to still another embodiment in the eighth aspect of theinvention, the image data characteristic extraction unit 70 divides thedigital image data into at least two or more equal small blocks andextracts the array pattern of the pixel values for each small block. Theimage data false alteration detection unit 71, on the other hand,detects a false alteration of the digital image data in the case wherethe array patterns of the pixel values of the small blocks extracted bythe image data characteristic extraction unit 70 coincide with eachother, as compared with the unique characteristic that the probabilityis very low that the array patterns of the pixel values of the smallblocks coincide with each other.

Yet another embodiment in the eighth aspect of the invention is suitablefor detecting a false alteration of the digital image acquired by adigital image data acquisition device having a CCD such as a digitalcamera or an image scanner. According to this embodiment, the image datacharacteristic extraction unit 70 extracts the pixel value of each pixelof the digital image data. The image data false alteration detectionunit 71, on the other hand, calculates a predicted pixel value for eachpixel of the digital image data by the interpolation calculation basedon the CCD matrix array of the digital image data acquisition devicefrom the pixel value of each pixel of the digital image data extractedby the image data characteristic extraction unit 70, and in the casewhere the pixel value of each pixel extracted by the image datacharacteristic extraction unit 70 fails to coincide with a correspondingpredicted pixel value, a false alteration of the digital image data isdetected.

FIG. 34 is a flowchart for a digital image data false alterationdetection program according to an embodiment in the ninth aspect of theinvention. As shown in FIG. 34, with the digital image data falsealteration detection program according to this invention, a computerdetects focused areas in the image based on the digital image dataacquired by the digital image data acquisition device, and upondetermination that two or more detected areas exist and spaced from eachother by a predetermined distance, detects a false alteration of thedigital image data (step S1 in FIG. 34).

This embodiment is effective especially for detecting a false alterationof the digital image committed by the image synthesis process.

As a specific example, an explanation is given below about a case inwhich the digital image data false alteration detection programaccording to this invention is installed in a computer and used for adigital image actually picked up by a digital camera. FIG. 35 shows adigital image picked up by a digital camera and not falsely altered.FIG. 36 is a graph showing the frequency characteristic obtained byextracting and subjecting to FFT (fast Fourier transform) 16 by 16pixels in the focused area P4 in the image shown in FIG. 35 and using aHPF (high-pass filter). FIG. 37 is a graph showing the frequencycharacteristic obtained by extracting 16 by 16 pixels in the unfocusedarea P5 constituting the background in the image shown in FIG. 35 andprocessing them in similar manner to the area P4. Comparison betweenFIG. 36 and FIG. 37 shows that the spectrum of the high-frequency domainin the focused area is very strong.

FIG. 38 shows an image falsely altered by the process of synthesizingthe image shown in FIG. 35 with another image. FIG. 39 is a graphshowing the frequency characteristic obtained by extracting 16 by 16pixels in the area P6 of another image synthesized with the image shownin FIG. 38 and processing them in a similar manner to the area P4 shownin FIG. 35. FIG. 39 indicates that the area P6 also has a very strongspectrum of high-frequency domain and the image is focused. In the imageshown in FIG. 38, therefore, two focused areas (areas P4 and P6) arespaced from each other by a predetermined distance, thereby indicatingthat the image is synthesized. Thus, a false alteration is detected.

FIG. 40 is a block diagram showing a general configuration of a digitalimage data false alteration detection apparatus according to anembodiment in the tenth aspect of the invention. The digital image datafalse alteration detection apparatus according to this inventioncomprises a programmed computer, and as shown in FIG. 40, furthercomprises a focused area detection unit 80 for detecting a focused areain an image based on the digital image data acquired by the digitalimage data acquisition device and a false alteration detection unit 81for detecting a false alteration of the digital image data in the casewhere the existence of a plurality of focused areas spaced from eachother by a predetermined distance is determined from the positions ofthe particular areas in the image detected by the focused area detectionunit 80.

INDUSTRIAL APPLICABILITY

As described above, according to this invention, the presence or absenceof a data alteration is detected by utilizing the characteristicinherent to the analog-to-digital conversion process of the digital dataacquisition device. Even in an open system, therefore, a false dataalteration can be positively detected. Also, the need of a device forburying the data in advance or extracting the data buried is eliminated.Thus, this invention greatly contributes to overcoming the problem offalse alteration of the digital data which is expected to be posed bythe future development of the IT technology.

1. A digital data false alteration detection program for causing acomputer to detect the false alteration of the digital data acquired bya digital data acquisition device including a light detector or a sounddetector and an A/D converter, characterized in that said computer iscaused to execute: (a) a step of dividing said digital data into atleast two smaller block data, (b) a step of extracting noises inherentto said digital data acquisition device for each of said small blockdata, (c) a step of calculating the correlation of said noises betweenadjacent ones of said small block data, and (d) a step of detectingsmall block data having a noise correlation lower than a levelpredetermined for the surrounding small block data, as a falsely altereddata.
 2. The digital data false alteration detection program accordingto claim 1, characterized in that said step (b) includes a step ofconverting each of said small block data into a frequency domain andextracting the high-frequency component of said each small block data asa noise inherent to said digital data acquisition device.
 3. The digitaldata false alteration detection program according to claim 1,characterized in that said step (b) includes a step of converting eachof the small block data into a frequency domain and extracting aspecific high-frequency component of said each small block data as anoise inherent to said digital data acquisition device.
 4. The digitaldata false alteration detection program according to claim 1,characterized in that said step (c) includes a step of calculating anaccumulated value of said noise for said each of the small block dataand calculating the correlation of said noise from the difference of theaccumulated value of said noise between adjacent ones of said smallblock data.
 5. A digital data false alteration detection apparatus fordetecting a false alteration of the digital data acquired by a digitaldata acquisition device including a light detector or a sound detectorand an A/D converter, comprising: a data divider for dividing saiddigital data into at least two small block data; a noise extraction unitfor extracting a noise inherent to said digital data acquisition devicefor each of said small block data; and a false alteration detection unitfor calculating the correlation of said noise between adjacent ones ofsaid small block data and detecting the small block data with said noisecorrelation lower than a level predetermined for the surrounding smallblock data, as a false data.
 6. The digital data false alterationdetection apparatus according to claim 5, characterized in that saidnoise extraction unit converts each of said small block data into afrequency domain and extracting the high-frequency component of saideach small block data as a noise inherent to said digital dataacquisition device.
 7. The digital data false alteration detectionapparatus according to claim 5, characterized in that said noiseextraction unit converts each of said small block data into a frequencydomain and extracting a specific high-frequency component of said eachsmall block data as a noise inherent to said digital data acquisitiondevice.
 8. The digital data false alteration detection apparatusaccording to claim 5, characterized in that said data divider is adaptedto divide said small block data into data of an arbitrary size.
 9. Thedigital data false alteration detection apparatus according to claim 5,characterized in that said false alteration detection unit calculates anaccumulated value of said noise for each of said small block data andcalculating the correlation of said noise from the difference of theaccumulated value of said noise between adjacent ones of said smallblock data.
 10. The digital data false alteration detection apparatusaccording to claim 5, characterized in that said data divider is adaptedto divide said digital data at an arbitrary position.
 11. A digitalimage data false alteration detection program for causing a computer todetect a false alteration of the digital image data acquired by adigital image data acquisition device including an A/D converter,characterized in that said computer is caused to execute: (a) a step ofextracting the noise of the pixel value of said digital image data; and(b) a step of comparing said extracted noise characteristic with thenoise characteristic inherent to the A/D conversion process of saiddigital image data acquisition device, and based on the result ofcomparison, detecting a false alteration of the digital image dataacquired by said digital image data acquisition device.
 12. A digitalimage data false alteration detection apparatus for detecting a falsealteration of the digital image data acquired by a digital image dataacquisition device including an A/D converter, comprising: an image datanoise characteristic extraction unit for extracting the noisecharacteristic of the pixel value of said digital image data; and animage data false alteration detection unit for comparing the noisecharacteristic extracted by said image data noise characteristicextraction unit with the noise characteristic inherent to the A/Dconversion process of said digital image data acquisition device andbased on the result of comparison, detecting a false alteration of thedigital image data acquired by said digital image data acquisitiondevice.
 13. A digital image data false alteration detection program forcausing a computer to detect a false alteration of the digital imagedata acquired by said digital image data acquisition device including anA/D converter, characterized in that said computer is caused to execute:(a) a step of extracting the noise characteristic of the pixel value ofsaid digital image data; and (b) a step of dividing said digital imagedata into at least two small blocks, comparing the noise characteristicsbetween adjacent ones of said small blocks and upon development of ananomaly between the compared noise characteristics, detecting a falsealteration of the digital image data acquired by said digital image dataacquisition device.
 14. A digital image data false alteration detectionapparatus for detecting a false alteration of the digital image dataacquired by a digital image data acquisition device including an A/Dconverter, comprising: a noise characteristic extraction unit forextracting the noise characteristic of the pixel value of said digitalimage data; and a false alteration detection unit for dividing saiddigital image data into at least two small blocks, comparing the noisecharacteristics between adjacent ones of said small blocks based on thenoise characteristic extracted by said noise characteristic extractionunit and upon development of an anomaly between the compared noisecharacteristics, detecting a false alteration of the digital image dataacquired by said digital image data acquisition device.
 15. A digitalimage data false alteration detection program for causing a computer todetect a false alteration of the digital image data acquired by adigital image data acquisition device including an A/D converter,characterized in that said computer is caused to execute: (a) a step ofextracting the characteristic about the pixel value of said digitalimage data; and (b) a step of comparing said extracted characteristicwith the characteristic inherent to the pixel value of said digitalimage data in the A/D conversion process of said digital image dataacquisition device and based on the result of comparison, detecting afalse alteration of the digital image data acquired by said digitalimage data acquisition device.
 16. The digital image data falsealteration detection program according to claim 15, characterized inthat said step (a) includes a step of extracting a histogram about thepixel value of said acquired digital image data, and said step (b)includes a step of comparing said extracted histogram with the histograminherent to the pixel value of the digital image data in the A/Dconversion process of said digital image data acquisition device, and inthe case where said inherent histogram assumes a continuous value whilesaid extracted histogram assumes a discontinuous value, detecting afalse alteration of the digital image data acquired by said digitalimage data acquisition device.
 17. The digital image data falsealteration detection program according to claim 15, characterized inthat said step (a) includes a step of dividing said acquired digitalimage data into at least two equal small blocks and extracting an arraypattern of the pixel values for said each small block, and said step (b)includes a step of detecting a false alteration of said digital imagedata in the case where the array patterns of the pixel values of thesmall blocks extracted in said step (a) are coincident with each other,as compared with said inherent characteristic that the probability thatthe array patterns of the pixel values of said small blocks coincidewith each other is very low.
 18. The digital image data false alterationdetection program according to claim 15, characterized in that saiddigital image data acquisition device includes an image acquisitiondevice having a CCD, and said step (a) includes a step of extracting thepixel value of each pixel of said acquired digital image data, whilesaid step (b) includes a step of calculating a predicted pixel value ofeach pixel of said digital image data by the interpolation calculationbased on the CCD matrix array of said digital image data acquisitiondevice from the pixel value of each pixel of the digital image dataextracted in said step (a), and in the case where the pixel value ofeach pixel extracted in said step (a) fails to coincide with acorresponding predicted pixel value, detecting a false alteration ofsaid digital image data.
 19. A digital image data false alterationdetection apparatus for detecting a false alteration of the digitalimage data acquired by a digital image data acquisition device includingan A/D converter, comprising: an image data characteristic extractionunit for extracting the characteristic about the pixel value of saiddigital image data; and an image data false alteration detection unitfor comparing the characteristic extracted by said image datacharacteristic extraction unit with the characteristic inherent to thepixel value of the digital image data in the A/D conversion process ofsaid digital image data acquisition device and based on the result ofcomparison, detecting a false alteration of said acquired digital imagedata.
 20. The digital image data false alteration detection apparatusaccording to claim 19, characterized in that said image datacharacteristic extraction unit extracts a histogram about the pixelvalue of said acquired digital image data, and in that said image datafalse alteration detection unit compares the histogram extracted by saidimage data characteristic extraction unit with the histogram inherent tothe pixel value of the digital image data in the A/D conversion processof said digital image data acquisition device, and in the case wheresaid inherent histogram assumes a continuous value while said histogramextracted by said image data characteristic extraction unit assumes adiscontinuous value, detects a false alteration of the digital imagedata acquired by said digital image data acquisition device.
 21. Thedigital image data false alteration detection apparatus according toclaim 19, characterized in that said image data characteristicextraction unit divides said acquired digital image data into at leasttwo equal small blocks and extracts the array pattern of the pixelvalues of said each small block, and in that said image data falsealteration detection unit detects a false alteration of said digitalimage data in the case where the array patterns of the pixel values ofthe small blocks extracted by said image data characteristic extractionunit are coincident with each other, as compared with said inherentcharacteristic that the probability that the array patterns of the pixelvalues of said small blocks coincide with each other is very low. 22.The digital image data false alteration detection apparatus according toclaim 19, characterized in that said digital image data acquisitiondevice includes an image acquisition device having a CCD, and said imagedata characteristic extraction unit extracts the pixel value of eachpixel of the acquired digital image data, while said image data falsealteration detection unit calculates a predicted pixel value of eachpixel of said digital image data by the interpolation calculation basedon the CCD matrix array of said digital image data acquisition devicefrom the pixel value of each pixel of the digital image data extractedby said image data characteristic extraction unit, and in the case wherethe pixel value of each pixel extracted by said image datacharacteristic extraction unit fails to coincide with a correspondingpredicted pixel value, detects a false alteration of said digital imagedata.
 23. A digital image data false alteration detection program forcausing a computer to detect a false alteration of the digital imagedata acquired by a digital image data acquisition device, characterizedin that said computer is caused to execute: a step of detecting focusedareas in an image based on said digital image data, and upondetermination that two or more areas are detected and spaced from eachother by at least a predetermined distance, detecting a false alterationof said digital image data.
 24. A digital image data false alterationdetection apparatus for detecting a false alteration of the digitalimage data acquired by a digital image data acquisition device,comprising: a focused area detection unit for detecting focused areas inan image based on said digital image data; and an alteration detectionunit for detecting a false alteration of said digital image data upondetermination, based on the positions, in said image, of said areasdetected by said focused area detection unit, that a plurality of theareas are detected and spaced from each other by a predetermineddistance.
 25. The digital data false alteration detection programaccording to claim 2, characterized in that said step (c) includes astep of calculating an accumulated value of said noise for said each ofthe small block data and calculating the correlation of said noise fromthe difference of the accumulated value of said noise between adjacentones of said small block data.
 26. The digital data false alterationdetection program according to claim 3, characterized in that said step(c) includes a step of calculating an accumulated value of said noisefor said each of the small block data and calculating the correlation ofsaid noise from the difference of the accumulated value of said noisebetween adjacent ones of said small block data.
 27. The digital datafalse alteration detection apparatus according to claim 6, characterizedin that said data divider is adapted to divide said small block datainto data of an arbitrary size.
 28. The digital data false alterationdetection apparatus according to claim 7, characterized in that saiddata divider is adapted to divide said small block data into data of anarbitrary size.
 29. The digital data false alteration detectionapparatus according to claim 6, characterized in that said falsealteration detection unit calculates an accumulated value of said noisefor each of said small block data and calculating the correlation ofsaid noise from the difference of the accumulated value of said noisebetween adjacent ones of said small block data.
 30. The digital datafalse alteration detection apparatus according to claim 7, characterizedin that said false alteration detection unit calculates an accumulatedvalue of said noise for each of said small block data and calculatingthe correlation of said noise from the difference of the accumulatedvalue of said noise between adjacent ones of said small block data. 31.The digital data false alteration detection apparatus according to claim8, characterized in that said false alteration detection unit calculatesan accumulated value of said noise for each of said small block data andcalculating the correlation of said noise from the difference of theaccumulated value of said noise between adjacent ones of said smallblock data.
 32. The digital data false alteration detection apparatusaccording to claim 6, characterized in that said data divider is adaptedto divide said digital data at an arbitrary position.
 33. The digitaldata false alteration detection apparatus according to claim 7,characterized in that said data divider is adapted to divide saiddigital data at an arbitrary position.
 34. The digital data falsealteration detection apparatus according to claim 8, characterized inthat said data divider is adapted to divide said digital data at anarbitrary position.
 35. The digital data false alteration detectionapparatus according to claim 9, characterized in that said data divideris adapted to divide said digital data at an arbitrary position.